Membrane-assisted solvent extraction of seven phenols combined with large volume injection-gas chromatography-mass spectrometric detection

Membrane-assisted solvent extraction (MASE) was applied for the determination of seven phenols (phenol, 2-chlorophenol, 2,4-dimethylphenol, 2,4-dichlorophenol, 4-chloro-3-methylphenol, 2,4,6-trichlorophenol and pentachlorophenol) with log Kow (octanol-water-partition-coefficient) between 1.46 (phenol) and 5.12 (pentachlorophenol) in water. The extraction solvents cyclohexane, ethyl acetate and chloroform were tested and ethyl acetate proved to be the best choice. The optimisation of extraction conditions showed the necessity of adding 5 g of sodium chloride to each aqueous sample to give a saturated solution (333 g/L). The pH-value of the sample was adjusted to 2 in order to convert all compounds into their neutral form. An extraction time of 60 min was found to be optimal. Under these conditions the recovery of phenol, the most polar compound, was 11%. The recoveries of the other analytes ranged between 42% (2-chlorophenol) and 98% (2,4-dichlorophenol). Calibration was performed using large volume injection (100 microL injection volume). At optimised conditions the limits of detection were between 0.01 and 0.6 microg/L and the relative standard deviation (n = 3) was on average about 10%. After the method optimisation with reagent water membrane-assisted solvent extraction was applied to two contaminated ground water samples from the region of Bitterfeld in Saxony-Anhalt, Germany. The results demonstrate the good applicability of membrane-assisted solvent extraction for polar analytes like phenols, without the necessity of derivatisation or a difficult and time-consuming sample preparation.     

Analysis of polycyclic aromatic hydrocarbons in water and beverages using membrane-assisted solvent extraction in combination with large volume injection-gas chromatography-mass spectrometric detection

Membrane-assisted solvent extraction (MASE) in combination with large volume injection-gas chromatography-mass spectrometry (LVI-GC-MS) was applied for the determination of 16 polycyclic aromatic hydrocarbons (PAHs) in aqueous samples. The MASE conditions were optimized for achieving high enrichment of the analytes from aqueous samples, in terms of extraction conditions (shaking speed, extraction temperature and time), extraction solvent and composition (ionic strength, sample pH and presence of organic solvent). Parameters like linearity and reproducibility of the procedure were determined. The extraction efficiency was above 65% for all the analytes and the relative standard deviation (RSD) for five consecutive extractions ranged from 6 to 18%. At optimized conditions detection limits at the ng/L level were achieved. The effectiveness of the method was tested by analyzing real samples, such as river water, apple juice, red wine and milk.     

Membrane-assisted solvent extraction of polychlorinated biphenyls in river water and other matrices combined with large volume injection-gas chromatography-mass spectrometric detection

Membrane-assisted solvent extraction was applied to the determination of polychlorinated biphenyls (PCBs) in aqueous samples. The apparatus of membrane-assisted solvent extraction consisted of a 20 ml headspace vial which was filled with 15 ml of the aqueous sample. The membrane bag was placed into the vial and the extraction took place in an agitator. After extraction, the analytes were transferred into the inlet of a gas chromatograph by large volume injection. A mass-selective detector was used. The whole procedure was fully automated. The work included optimization of the extraction conditions (stirring rate and extraction time) and the influence of matrix effects like salt addition and the presence of organic solvents was studied. Calibration was performed using injection volumes of 100 and 400 microl. Several parameters like linearity and reproducibility of the procedure were determined. At optimized conditions detection limits in the ng/l range were achieved. The effectiveness of the method towards real samples was tested by analyzing river water, white wine and apple juice.     

Determination of PAHs in airborne particles by accelerated solvent extraction and large-volume injection-gas chromatography-mass spectrometry

A sensitive and automated method is presented for the determination of polycyclic aromatic hydrocarbons (PAHs) in airborne particulate matter. The procedure includes extraction of PM10-bound PAHs by accelerated solvent extraction (ASE) followed by gel permeation chromatography (GPC) clean-up, and large-volume programmable temperature vaporizer (PTV-LV) injection coupled to GC-MS. The limit of detection (LOD) of the whole method, based on a signal-to-noise ratio (S/N) of 3:1, ranged from 0.26 pg m⁻³ to 3 pg m⁻³ when air volumes of 760 m³ are collected.The hexane-acetone mixture (1:1, v/v) gave the best recoveries when ASE parameters were fixed at 125 °C, 1500 psi, and a total time of 10 min. The recoveries for all PAHs tested ranged from 96% to 103%, rates similar to those obtained by the Soxhlet reference method.To improve the sensitivity, 70 μL were injected. The PTV-LV injection settings were optimized using a statistical design of experiments, including a screening 2⁴ full factorial design and a further central composite design. A sensitivity increase from 10 to 50 times was achieved as compared with the conventional 2 μL splitless injection.The method was validated with the standard reference material SRM 1649a and applied to real PM10 samples from the monitoring network of the Regional Valencia Government (Spain).The analytical performance of the method shows that it is appropriate to monitor PAHs levels in ambient air according to European Union Directives. In addition, the method can be used when a high sensitivity is required.     

快速溶剂萃取-气相色谱-串联质谱法同时测定土壤中有机氯及有机磷农药

建立了快速溶剂萃取（ASE）-气相色谱-串联质谱（GC-MS/MS）同时分析土壤中8种有机氯农药（OCPs）和5种有机磷农药（OPPs）的方法。样品由正己烷-丙酮（1：1,v/v）溶液萃取,经无水硫酸钠脱水、氮吹仪浓缩后,采用硅胶（Si）固相萃取小柱进行净化,正己烷-丙酮（1：1,v/v）溶液进行洗脱,然后经HP-5MS色谱柱（30 m×0.25 mm×0.25 μm）分离,在电子轰击电离源下以多反应监测（MRM）模式进行检测,内标法定量。分析结果表明,13种目标物在1.00~100 μg/L范围内线性关系良好,相关系数（R）大于0.995;加标回收率为66.8%~88.4%,能够实现准确定量;日内精密度与日间精密度均小于10%。当取样量为10.0 g时,8种OCPs的方法检出限为0.02~0.04 μg/kg,5种OPPs的方法检出限为0.06~0.12 μg/kg,能够满足土壤农药残留的检测要求。     

Determination of polar organophosphorus pesticides in vegetables and fruits using liquid chromatography with tandem mass spectrometry: selection of extraction solvent

A method based on liquid chromatography (LC)-mass spectrometry (MS)/MS was developed for sensitive determination of a number of less gas chromatography (GC)-amenable organophosphorus pesticides (OPs; acephate, methamidophos, monocrotophos, omethoate, oxydemeton-methyl and vamidothion) in cabbage and grapes. For extraction, several solvents were evaluated with respect to the possibility of direct injection, matrix-induced suppression or enhancement of response, and extraction efficiency. Overall, ethyl acetate was the most favourable solvent for extraction, although a solvent switch was required. For some pesticide/matrix combinations, reconstitution of the residue after evaporation required special attention. Extracts were analysed on a C18 column with polar endcapping. The pesticides were ionised using atmospheric pressure chemical ionisation on a tandem mass spectrometer in multiple reaction monitoring mode. The final method is straightforward and involves extraction with ethyl acetate and a solvent switch to 0.1% acetic acid/water without further cleanup. The method was validated at the 0.01 and 0.5 mg/kg level, for both cabbage and grapes. Recoveries were between 80 and 101% with R.S.D. < 11% (n = 5). The limit of quantification was 0.01 mg/kg and limits of detection were between 0.001 and 0.004 mg/kg.     

Combining stir-bar sorptive extraction and large volume injection-gas chromatography-mass spectrometry for the determination of benzotriazole UV stabilizers in wastewater matrices

Stir‐bar sorptive extraction and liquid desorption followed by large volume injection‐gas chromatography coupled to mass spectrometry under selected ion monitoring mode acquisition (SBSE‐LD/LVI‐GC‐MS(SIM)) was applied for the determination of six benzotriazole UV stabilizers (Tinuvin P, Allyl‐bzt, Tinuvin 320, Tinuvin 326, Tinuvin 327 and Tinuvin 328) in wastewater matrices. Parameters affecting the performance of extraction and desorption steps were thoroughly evaluated using uni‐ and multivariate optimization strategies, based on the use of experimental factorial designs. Assays performed with stir bars, coated with 24 μL of polydimethylsiloxane, on 25 mL of ultra‐pure water samples spiked at the 0.5 ng/mL level, yielded recoveries ranging from 47.9±1.4% (Tinuvin P) to 103.1±3.6% (Tinuvin 326), under optimized experimental conditions. When applied to complex matrices (e.g. wastewater), the methodology showed also excellent linear dynamic ranges (0.02–10.00 ng/mL) for the six benzotriazole UV stabilizers studied with correlation coefficients higher than 0.9970, limits of quantification in between 0.004 and 0.015 ng/mL, suitable repeatability (RSD<12.7%) and reproducibility (RSD<4.5%). The application of the proposed methodology to urban sewage waters from Spain and Portugal wastewater plants revealed the presence of low contents of some benzotriazole UV stabilizers.     

Determination of various pesticides using membrane extraction discs and gas chromatography-mass spectrometry

A method for the determination of a group of pesticides in water by gas chromatography-mass spectrometry with electron impact ionization was developed. The preconcentration of 500 ml of water with C₁₈ and styrenedivinylbenzene (SDB) allowed the determination of pesticides at low-μg/1 levels. The use of SDB membrane extraction discs gave a large increase in the recovery of aldrin compared with the value obtained with C₁₈ discs. With SDB discs the recoveries were> 85% for most compounds. The limits of detection were between 0.06 and 0.2 μg/1 in the full-scan mode. The mass spectra under positive and negative chemical ionization conditions with methane were also obtained and higher sensitivity with negative chemical ionization was obtained for most compounds.     

Miniaturized membrane-assisted solvent extraction combined with gas chromatography/electron-capture detection applied to the analysis of volatile organic compounds

A new module of membrane-assisted solvent extraction (MASE) with miniaturized membrane bags was applied to the determination of seven volatile organic compounds (VOCs): chloroform, 1,1,1-trichloroethane, trichloroethylene, 1,1,2-trichloroethane, tetrachloroethene, 1,1,1,2-tetrachloroethane, 1,1,2,2-tetrachloroethane with boiling points between 61 and 147 degrees C in aqueous samples. Different from the known procedure the new, shortened membrane bags were filled with 100 microl of an organic solvent. The membrane bags were placed in a 20 ml headspace vial and filled with 15 ml of the aqueous sample. The vial was transferred into an autosampler where it was stirred for a definite time at elevated temperature. After the extraction, 1 microl of the organic extract was transferred into the spilt/splitless injector of a GC system equipped with an electron-capture detector. This work included optimization of the membrane device, the determination of the optimized extraction conditions such as stirring rate, extraction time and the impact of salt addition. The validation of the method involved repeatability, recovery and detection limit studies, followed of its application towards real water samples. The repeatability, expressed as the relative standard deviation of the peak areas of six extractions was below 10%. The detection limits (LODs) were between 5 ng/l (tetrachloroethene) and 50 ng/l (chloroform). Calibration was performed in a range from 5 ng/l to 150 microg/l, since the concentration in the aqueous samples was expected quite various in this concentration range. Five river water samples of Bitterfeld, Saxony-Anhalt, Germany were analyzed with miniaturized-MASE and the results were compared with those obtained with Headspace-Analysis. The method can be fully automated and moreover, it allows the simultaneous determination of volatile and semi volatile compounds.     

Determination of organophosphorus pesticides by gas chromatography with mass spectrometry using a large‐volume injection technique after magnetic extraction

A fast and efficient method was developed for the extraction and determination of organophosphorus pesticides in water samples. Organophosphorus pesticides were extracted by solid‐phase extraction using magnetic multi‐walled carbon nanotubes and determined by gas chromatography with ion‐trap mass spectrometry. Parameters affecting the extraction were investigated. Under optimum conditions of the method, 10 mg magnetic multi‐walled carbon nanotubes were added into 10 mL sample. After 2 min, adsorbent particles settled at the bottom of test tube with a magnet. After removing aqueous supernatant, the analytes were desorbed with acetonitrile. Then, 70 μL of acetonitrile phase was injected into the gas chromatography and mass spectrometry system that had an ion‐trap analyzer. To achieve high sensitivity, the large‐volume‐injection technique was used with a programmed temperature vaporization inlet, and the ion‐trap mass spectrometer was operated in single ion storage mode. Under the best conditions, the enrichment factors and extraction recoveries were in the range of 113–124 and 74–103%, respectively. The limits of detection were between 3 and 15 ng/L, and the relative standard deviations were < 10%. This method was successfully used for the determination of organophosphorus pesticides in dam water, lagoon water, and river water samples with good reproducibility and recovery.     

Determination of triazines and organophosphorus pesticides in water samples using solid-phase extraction.

Octadecyl (C18)-bonded porous silica was evaluated for the extraction of triazine and organophosphorus pesticides from natural water. The extraction results showed an effective performance when 11 of water was passed through small glass columns containing 500 mg of 50-100-microns C18 bonded porous silica. The adsorbed compounds were removed with ethyl acetate, evaporated to 200 microliters and determined by gas chromatography. The overall average recoveries were greater than 85% except for dimethoate and trichlorfon. Application of this procedure to the analysis of natural water samples gave results that agree well with those obtained by solvent extraction methods.     

Multiresidue determination of organophosphorus pesticides in ginkgo leaves by accelerated solvent extraction and gas chromatography with flame photometric detection

A rapid and simple method using accelerated solvent extraction and solid-phase extraction cleanup was developed and validated for the determination of 15 organophosphorus pesticides in ginkgo leaves by capillary gas chromatography with flame photometric detection. The pesticides were extracted at 100 degrees C under 1500 psi pressure in <20 min. The average recovery from 10 g ginkgo leaves, fortified at 3 levels ranging from 0.05 to 1.00 mg/kg, was 95.2% with a relative standard deviation of 4.6%. The limits of detection ranged from 1.11 x 10(-3) mg/kg (dimethoate) to 4.44 x 10(-3) mg/kg (dichlorvos). The proposed method showed acceptable accuracy and precision while minimizing environmental concerns, time, and labor. Furthermore, the method could be easily applied to the monitoring of these 15 organophosphorus pesticides in ginkgo leaves.     

Determination of carbamate pesticides using micro-solid-phase extraction combined with high-performance liquid chromatography

We describe a simple and sensitive porous polypropylene membrane-protected micro-solid-phase extraction (μ-SPE) approach for the sample preparation and determination of carbamate pesticides in soil samples by high-performance liquid chromatography. The μ-SPE device consisted of C₁₈ sorbent held within a porous polypropylene envelope. In order to achieve optimum performance, several extraction parameters were optimized. Under the most favorable conditions, the extraction efficiency of the μ-SPE was very high, with detection limits in the range of 0.01–0.40 ng g⁻¹. This is more than two orders of magnitude lower than the limits obtained by the United States Environmental Protection Agency Methods 8321A and 8318. A linear relationship was obtained for each analyte in the range of 2 and 200 ng g⁻¹. The relative standard deviation for the analysis of aged soil samples spiked at 5 ng g⁻¹ was ≤11%. The reproducibility of separate μ-SPE device used for experiments was satisfactory (relative standard deviations ranged from 4 to 11%), indicating that the method is reliable for routine environmental analysis.     

加速溶剂萃取/凝胶渗透色谱－固相萃取净化、气相色谱－质谱法测定茶叶中残留的33种农药

建立了茶叶中有机磷、有机氯、拟除虫菊酯类共33种农药残留的分析方法。样品以丙酮-二氯甲烷(体积比为1:1)为提取剂经加速溶剂方法萃取,提取液用凝胶渗透色谱净化除去大部分的色素、脂类和蜡质,再用Carb-NH2小柱和Florisil小柱净化。采用气相色谱法分析、外标法定量、气相色谱-质谱法（GC-MS）定性。加标水平为0.05 mg/kg时,大部分农药的回收率为70%~120%,相对标准偏差小于20%。方法的检测限为0.005～0.05 mg/kg (以10倍信噪比计)。该方法的提取效率高,准确灵敏,目前已应用于出口茶叶中农药残留的日常检测。大量实际样品的检测结果表明,此方法适于出口茶叶中农药残留检测实际工作的需要。     

固相微萃取-气相色谱-质谱联用分析环境水样中痕量有机磷农药

研究了固相微萃取(SPME) 气相色谱 质谱联用(GC MS)同时测定环境水样中二嗪农、甲基对硫磷、对硫磷和水胺硫磷4种有机磷农药(OPPs)的分析方法。选择聚丙烯酸酯(PA)萃取纤维,对SPME的条件如萃取时间、萃取溶液的pH值和离子强度、解吸温度、解吸时间和GC MS的条件进行了优化。对二嗪农和水胺硫磷方法线性范围为0.001～10μg L,对甲基对硫磷和对硫磷方法线性范围为0.001～100μg L。二嗪农、甲基对硫磷、对硫磷、水胺硫磷的检出限分别为0.015,0.020,0.013和0.039μg L。分析加标自来水、矿泉水和湖水样品,回收率在89.0%～102%之间,RSD在2.1%～14.1%之间。适合于环境水样中痕量OPPs的快速分析。     

大体积搅拌棒吸附萃取技术与热脱附-气相色谱-质谱法测定地表水中多环芳烃

基于搅拌棒吸附萃取(SBSE)技术建立了气相色谱-质谱测定地表水中16种多环芳烃(PAHs)的分析方法。该法采用多搅拌吸附棒同时富集,依次热脱附冷聚焦后进样的方式有效解决了搅拌棒吸附时间长、富集水样体积小等问题。优化后的结果表明,在0.2~10 ng/L范围内(萘为0.5~10 ng/L范围),16种PAHs的线性关系良好,相关系数(r)均0.99,方法检出限(MDL)为0.03~0.20 ng/L(萘为0.50 ng/L)。用该方法对钱塘江流域地表水进行测定,共检测出11种PAHs,含量为0.13~1.57 ng/L,不同添加水平下的加标回收率为75.6%~108.9%。该法可应用于地表水样品中该类物质的超痕量检测。     

Multi-residue determination of organophosphorus and organochlorine pesticides in environmental samples using solid-phase extraction with cigarette filter followed by gas chromatography-mass spectrometry

A solid‐phase extraction (SPE) method was developed to extract 14 pesticides simultaneously from environment samples using cigarette filter as the sorbent before gas chromatography‐mass spectrometry (GC‐MS) analysis. Parameters influencing the extraction efficiency, such as the sample loading flow rate, eluent and elution volume, were optimized. The optimum sample loading rate was 3 mL/min, and the retained compounds were eluted with 6 mL of eluent at 1 mL/min under vacuum. Good linearity was obtained for all the 14 pesticides (r²>0.99) from 0.1 to 20 μg/L for water and from 2 to 400 μg/kg for soil samples. The detection limits (signal‐to‐noise=3) of the proposed method ranged from 0.01 to 0.20 μg/L for water samples and from 0.42 to 6.95 μg/kg for soil samples. The developed method was successfully applied for determination of the analytes in real environmental samples, and the mean recoveries ranged from 76.4 to 103.7% for water samples and from 79.9 to 105.3% for soil samples with the precisions (relative standard deviation) between 2.0 and 13.6%.     

羟基化多壁碳纳米管分散固相萃取-气相色谱-质谱法测定茶叶中21种有机磷农药

建立了用羟基化多壁碳纳米管(MWCNTs-OH)、N-丙基乙二胺键合固相吸附剂(PSA)和MgSO₄作为吸附剂的改进QuEChERS-气相色谱-质谱快速检测茶叶中21种有机磷农药的方法。茶叶中残留的农药经正己烷-丙酮(2 : 1, v/v)混合溶剂提取,以MWCNTs-OH、PSA和MgSO₄去除杂质,离心、过滤后经气相色谱-电子轰击源质谱测定,外标法定量。结果表明,目标化合物在0.01~0.50 mg/kg范围内的线性关系良好。空白茶叶样品在低、中、高3个添加水平下的平均回收率为81.5%~109.4%,相对标准偏差(n=5)为2.3%~10.6%,定量限为0.001~0.040 mg/kg。该方法操作简单、快速、灵敏、成本低,能满足茶叶中常见有机磷农药残留的检测要求。     

磁固相萃取-气相色谱-火焰光度检测联用测定果汁中的有机磷农药

制备了苯乙烯（St）和甲基丙烯酸（MAA）共聚物改性的磁性微球Fe₃O₄@P（St-co-MAA）,并将其作为磁固相萃取吸附剂,建立了磁固相萃取（MSPE）-气相色谱（GC）-火焰光度检测（FPD）联用分析有机磷农药（OPPs）残留的新方法。以5种有机磷农药（二嗪农、甲基毒死蜱、杀螟硫磷、毒死蜱和喹硫磷）为目标分析物,考察并优化了吸附和解吸条件,确定了最佳实验条件。在最优的实验条件下,方法对5种OPPs的检出限（S/N=3）为0.013~0.305 μg/L,方法的相对标准偏差（RSD,n=7）为3.1%~8.8%,富集倍数为406~951,线性范围达3个数量级。将该方法应用于新鲜番茄汁、草莓汁样品中的OPPs残留分析,加标回收率为85.4%~118.9%。该方法具有检出限低、分析速度快、富集倍数高等优点,为有机磷农药的残留分析提供了新的技术平台。     

Determination of pesticides in river water using rotating disk sorptive extraction and gas chromatography-mass spectrometry

The rotating disk sorptive extraction (RDSE) technique was applied to the determination of pesticides in aqueous samples. Pesticides of different polarities were considered in this study: chlorpyrifos, diazinon, fenvalarate, cyhalothrin, cypermethrin, lindane and malathion. The sorptive/desorptive behavior of the pesticides was studied using a rotating disk containing a polydimethylsiloxane (PDMS) phase on one of its surfaces. The analyte polarity was a significant factor in the extraction time; shorter extraction times were required for the more apolar pesticides. The optimum variables for the extraction of all analytes were: extraction time of 3 h, sample volume of 25 mL, rotational velocity of the disk 1250 rpm, desorption time of 30 min using methanol. For pesticides with values of Log K_ow > 4, the extraction time can be reduced to 30 min for a quantitative extraction. Under these conditions, recoveries between 76% and 101% were obtained for the target pesticides, and the repeatability of the methodology, expressed as relative standard deviation, was determined to be between 10% and 20%. Additionally, the limits of detection of the analytes were lower than 3.1 μg L⁻¹. The extraction method developed using the RDSE was compared to a stir bar sorptive extraction (SBSE) under the same conditions. It can be observed that the extraction using the rotating disk offers higher recoveries because of its higher PDMS volume and its higher surface area to volume ratio that allows for improved mass transfer.